Electronic package structure

ABSTRACT

An electronic package includes a lead frame structure having one or more structural features configured to improve board level reliability. In one embodiment, the structural feature comprises lead frame protrusions extending outward from the electronic package, which are configured to laterally engage solder structures used to attach the electronic package to a next level of assembly. In another embodiment, conductive bumps are attached to exposed portions of the lead frame in advance of next level assembly processes. In a further embodiment, the lead frame comprises laterally separated contact points for attaching an electron die and for attaching the electronic package to a next level of assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2015-0029706 filed on Mar. 3, 2015 in the Korean IntellectualProperty Office, and all the benefits accruing therefrom under 35 U.S.C.§119, the contents of which in its entirety are herein incorporated byreference.

BACKGROUND

The present invention relates, in general, to electronics, and moreparticularly, to semiconductor packages, structures thereof, and methodsof forming semiconductor packages.

Electronic devices, such as semiconductor dies are conventionallyenclosed in package structures that protect the semiconductor die fromhostile environments and that enable electrical interconnection betweenthe semiconductor die and a next level of assembly, such as a printedcircuit board (“PCB”) or motherboard. The elements of a typical packagestructure include a conductive leadframe or substrate, an integratedcircuit or semiconductor die, conductive structures, such as bond wiresor solder balls that electrically connect pads on the semiconductor dieto individual leads of the leadframe or substrate, and a hard plasticencapsulant material that covers the other components and forms anexterior of the semiconductor package commonly referred to as thepackage body. Portions of the individual leads are configured toelectrically connect the package structure to the next level assembly.

In the past, certain reliability issues have plagued packaged electronicdevices particularly in chip-scale packaged electronic devices having ahigh density of interconnects in a small footprint package. Suchreliability issues have included, for example, poor bonding between thepackage electronic device and solder materials used to connect thepackaged electronic device to a next level assembly and as well as otherstress induced failures.

Accordingly, it is desirable to have a structure and method for formingpackaged electronic devices that reduce the occurrence of reliability,such as those described previously. It is further desirable for thestructure and method to be cost effective and manufacturable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional view of an electronic package inaccordance with an embodiment of the present invention;

FIG. 1B illustrates a cross-sectional view of the electronic package ofFIG. 1A attached to a next level of assembly in accordance with anembodiment of the present invention;

FIG. 2A illustrates a cross-sectional view of an electronic package inaccordance with another embodiment of the present invention;

FIG. 2B illustrates a cross-sectional view of the electronic package ofFIG. 2A attached to a next level of assembly in accordance with anembodiment of the present invention;

FIG. 3A illustrates a perspective plan view of an electronic package inaccordance with a further embodiment of the present invention; and

FIG. 3B illustrates a partial cross-sectional view of the electronicpackage of FIG. 3A taken along reference line 1-1′ of FIG. 3A attachedto a next level of assembly in accordance with an embodiment of thepresent invention.

For simplicity and clarity of illustration, elements in the figures arenot necessarily drawn to scale, and the same reference numbers indifferent figures denote generally the same elements. As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items. In addition, the terminology used herein isfor the purpose of describing particular embodiments only and is notintended to be limiting of the disclosure. As used herein, the singularforms are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, numbers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,numbers, steps, operations, elements, components, and/or groups thereof.It will be understood that, although the terms first, second, etc. maybe used herein to describe various members, elements, regions, layersand/or sections, these members, elements, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one member, element, region, layer and/or section fromanother. Thus, for example, a first member, a first element, a firstregion, a first layer and/or a first section discussed below could betermed a second member, a second element, a second region, a secondlayer and/or a second section without departing from the teachings ofthe present disclosure. Additionally, descriptions and details ofwell-known steps and elements are omitted for simplicity of thedescription. It will be appreciated by those skilled in the art thatwords, during, while, and when as used herein related to circuitoperation are not exact terms that mean an action takes place instantlyupon an initiating action but that there may be some small butreasonable delay, such as propagation delay, between the reaction thatis initiated by the initial action. Additionally, the term while means acertain action occurs at least within some portion of a duration of theinitiating action. The use of word about, approximately or substantiallymeans a value of an element is expected to be close to a state value orposition. However, as is well known in the art there are always minorvariances preventing values or positions from being exactly stated.Unless specified otherwise, as used herein the word over or on includesorientations, placements, or relations where the specified elements canbe in direct or indirect physical contact. Unless specified otherwise,as used herein the word overlapping includes orientations, placements,or relations where the specified elements can at least partly coincideor align in the same or different planes. It is further understood thatthe embodiments illustrated and described hereinafter suitably may haveembodiments and/or may be practiced in the absence of any element thatis not specifically disclosed herein.

DETAILED DESCRIPTION OF THE DRAWINGS

The present description includes, among other features, an electronicpackage structure comprising a substrate. The substrate includes a leadframe configured with one or more structural features configured toimprove board level reliability of the electronic package. In oneembodiment, the lead frame includes protrusions that extend outward froma surface of the electronic package. The protrusions are configured tolaterally engage conductive connective structures, such as solder balls.In another embodiment, conductive bumps are attached to exposed portionsof the lead frame in advance of attaching the electronic packagestructure to a next level of assembly. In a further embodiment, the leadframe is configured with difference points of contact for attaching anelectronic die to the lead frame and for attaching the lead frame to thenext level of assembly. More particularly, the points of contact arelaterally separated from each other to, among other things, reduce thevertical concentration of stress regions in the electronic packagestructure.

In one embodiment, the electronic package structure comprises asubstrate. The substrate comprises a die pad having die pad top surfaceand an opposing die pad bottom surface, wherein the die pad comprises aconductive material. A plurality of leads are laterally spaced apartfrom the die pad, and a substrate encapsulant is interposed between thedie pad and the plurality of leads, wherein the substrate encapsulanthas a substrate top surface and an opposing substrate bottom surface,and wherein the die pad and plurality of leads protrude outward from thesubstrate bottom surface. An electronic die is electrically coupled tothe die pad and the plurality of leads and a package body encapsulatesthe electronic die and the substrate top surface, wherein the substratebottom surface is exposed to the outside.

In another embodiment, the electronic package comprises a substrate. Thesubstrate comprises a die pad having die pad top surface and an opposingdie pad bottom surface, wherein the die pad comprises a conductivematerial. A plurality of leads are laterally spaced apart from the diepad each lead having a lead top surface and an opposing lead bottomsurface. A substrate encapsulant is interposed between the die pad andthe plurality of leads, wherein the substrate encapsulant has asubstrate top surface and an opposing substrate bottom surface.Conductive bumps are disposed on the die pad bottom surface and the leadbottom surfaces. An electronic die is electrically coupled to the diepad and the plurality of leads and a package body encapsulating theelectronic die and the substrate top surface, wherein the substratebottom surface is exposed to the outside. In one embodiment, the die padbottom surface and lead bottom surfaces can be substantially co-planarwith the substrate bottom surface

In a still further embodiment, the electronic package structurecomprises a substrate including a die pad and a plurality of leadsspaced apart from the die pad. An electronic die is electricallyconnected to the die pad and the plurality of leads. an encapsulantstructure encapsulating the substrate and the electronic die, wherein abottom surface of the die pad and bottom surfaces of the plurality ofleads are exposed to the outside, wherein the electronic die is attachedto first portions of the plurality of leads to define first connectionpoints, and wherein the plurality of leads comprise second portionsattached to the first portions, wherein the second portions areconfigured to define second connection points for attaching to a nextlevel of assembly, and wherein the first connection points and thesecond connection points are laterally separated.

In a still further embodiment, an electronic package structure comprisesa substrate, which comprises a die pad having die pad top surface and anopposing die pad bottom surface, wherein the die pad comprises aconductive material, a plurality of leads laterally spaced apart fromthe die pad each lead having a lead top surface and an opposing leadbottom surface, and a substrate encapsulant interposed between the diepad and the plurality of leads, wherein the substrate encapsulant has asubstrate top surface and an opposing substrate bottom surface. Anelectronic die electrically coupled to the die pad and the plurality ofleads, and a package body encapsulating the electronic die and thesubstrate top surface, wherein the substrate bottom surface is exposedto the outside. The substrate further comprises one or more structuralfeatures configured to improve board-level reliability, the one or morefeatures comprising one or more of: the die pad and the plurality ofleads configured to protrude outward from the substrate bottom surfacesuch that side surfaces of the die pad and side surfaces of theplurality of leads are exposed to the outside, conductive bumps disposedon the die pad bottom surface and the lead bottom surfaces, and/or atleast one lead comprising a first lead portion exposed to the outside ofthe substrate bottom surface and defining a first connection point forattaching the electronic package structure to a next level of assembly,and a second lead portion laterally extending towards the die pad andhaving a recessed bottom surface encapsulated by the substrateencapsulant, the second lead portion defining a second connection pointfor attaching to the electronic die, wherein the first connection pointis laterally separated from the second connection point.

Various aspects of the present description can be embodied in differentforms and should not be construed as being limited to the exampleembodiments set forth herein. Rather, these example embodiments of thedisclosure are provided to convey various aspects of the disclosure tothose of ordinary skill in the art.

FIG. 1A illustrates a cross-sectional view of an electronic package 100or electronic package structure 100, such as a semiconductor package100, in accordance with a first embodiment. FIG. 1B illustrates across-sectional view of semiconductor package 100 attached to a nextlevel of assembly, such as a circuit board or printed circuit board(“PCB”). In accordance with the present embodiment, semiconductorpackage 100 comprises a substrate 110, such as a lead frame 110 and asubstrate encapsulant 131, an electronic die 120, such as asemiconductor die 120, and package body 132. In one embodiment,substrate encapsulant 131 and package body 132 are configured as anencapsulant structure 130. In one embodiment, semiconductor die 120 canbe an integrated circuit device, such as an analog device, a logicdevice, a mixed-signal device, a power device, a discrete device, asensor device, an optical device, and/or a similar device as known tothose of skill in the art.

In one embodiment, lead frame 110 includes a die pad 111 having a diepad top surface 111 b and an opposing die pad bottom surface 111 c. Inone embodiment, die pad bottom surface 111 c comprises a continuous andsubstantially planar surface. Stated another way, die pad bottom surface111 c is formed without, is absent, or is free of intentionally formedrecessed portions or intentionally formed etched portions. In oneembodiment, die pad 111 comprises a conductive material such as copper,a copper alloy, a plated material, combinations thereof, or othermaterials as known to those of skill in the art. In one embodiment, diepad 111 comprises a substantially rectangular plate shape having foursides and four corners, which may be rounded. It is understood thatother shapes may be used as well. In some embodiments, the outerperiphery of die pad 111 can be reduced in thickness using, for example,etching or stamping techniques.

In one embodiment, lead frame 110 further comprises a plurality of leads112 spaced apart from die pad 111. Each lead 112 includes a lead topsurface 112 b and an opposing lead bottom surface 112 c. In oneembodiment, substrate encapsulant 131 encapsulates, covers, or encloses,for example, side portions of lead frame 110 except for portions thatprotrude outward from semiconductor package 100 as describedhereinafter. Substrate encapsulant 131 includes a substrate top surface131 a and an opposing substrate bottom surface 131 b. Semiconductor die120 is electrically connected to die pad 111 and plurality of leads 112.

In accordance with the present embodiment, semiconductor package 100 isconfigured to have a die pad protrusion 111 a, which protrudes orextends outside or away from substrate bottom surface 131 b or thebottom surface of encapsulant 130. Die pad protrusion 111 a isconfigured to better facilitate the attachment of semiconductor package100 to circuit board 10. More particularly, die pad protrusion 111 aprovides both vertical surfaces and a horizontal surface for engaging anattachment structure, such as a solder ball 20 as illustrated, forexample, in FIG. 1B. In some embodiments, die pad protrusion 111 a canhave a thickness d1 of up to about 10 microns particularly if the heightof semiconductor package is 100 is constrained. In other embodimentswhere package height or thickness is not constrained, thickness d1 canbe less than about 25 microns. In accordance with the presentembodiment, when semiconductor package 100 is attached to printedcircuit board 10, die pad protrusion 111 a is configured to facilitatesolder ball 20 surrounding the lateral surfaces or vertical surfaces ofdie pad protrusion 111 a in addition to its horizontal surface, whichallows for semiconductor package 100 to be more stably and reliablyconnected to circuit board 10 or other assembly structures.

In one embodiment, plurality of leads 112 are spaced apart from theperipheral edge segments (e.g., four sides) of die pad 111 and can bearranged in directions perpendicular to the peripheral edge segments.Each lead 112 is further spaced apart from other leads 112 so that theleads are electrically disconnected from each other in some embodiments.It is understood that in some embodiments, some of the leads 112 can beelectrically connected to each other depending on the systemapplication. In accordance with the present embodiment, each of leads112 includes a lead protrusion 112 a that protrudes or extends outsideor away from substrate bottom surface 131 b or the bottom surface ofencapsulant 130. In one embodiment, at least some of the leadprotrusions 112 a are formed to have a similar shape as die padprotrusion 111 a. Lead protrusions 112 a protrude to a lower portion ofeach of the plurality of leads 112 and to the outside of semiconductorpackage 100 as generally illustrated in FIG. 1A. In accordance with thepresent embodiment, lead protrusions 112 a are configured to betterfacilitate the attachment of semiconductor package 100 to circuit board10. More particularly, lead protrusions 112 a provide both verticalsurfaces and horizontal surfaces for engaging attachment structures,such as solder balls 20 as illustrated, for example, in FIG. 1B. In someembodiments, lead protrusions 112 a can have a thickness d1 of less thanabout 25 microns particularly if the height of semiconductor package is100 is constrained. In other embodiments where package height is notconstrained, thickness d1 can be greater than about 10 microns. Inaccordance with the present embodiment, when semiconductor package 100is attached to circuit board 10, lead protrusions 112 a are configuredto facilitate solder ball 20 surrounding the vertical surfaces orlateral surfaces of lead protrusions 112 a in addition to theirhorizontal surfaces, which allows for semiconductor package 110 to bemore stably and reliably connected to printed circuit board 10 or otherassembly structures.

In some embodiments, semiconductor die 120 has a plate like shape andhas a first surface 120 a and a second surface 120 b opposite to firstsurface 120 a. Semiconductor die 120 includes a plurality of conductivepads 121 formed on first surface 120 a. In some embodiments,semiconductor die 120 may include a protection layer (not shown) formedto cover the first surface 120 a of the semiconductor die 120 butleaving plurality of conductive pads 121 exposed to the outside.Plurality of conductive pads 121 can comprise aluminum, an aluminumalloy, copper, or other materials as known to those of skill in the art.

In accordance with the present embodiment, semiconductor die 120 ismounted on the lead frame 110 such that first surface 120 a and theplurality of conductive pads 121 face the top surface of lead frame 110or substrate top surface 131 a. By way of example, conductive pads 121can be attached or connected to lead frame 110 using a plurality ofconductive bumps 122. In some embodiments, the width of semiconductordie 120 may be larger than the width of die pad 111 such that at least aportion of first surface 120 a overlaps at least portions of leads 112.In one embodiment, more than one conductive bump 122 connectssemiconductor die 120 to die pad 111 as illustrated, for example, inFIGS. 1A and 1B.

Encapsulant 130 encapsulates lead frame 110 and semiconductor die 120 inorder to protect exposed portions of lead frame 110 and semiconductordie 120 from external environments. In accordance with the presentembodiment, encapsulant 130 includes a first encapsulant 131 orsubstrate encapsulant 131 encapsulating the lead frame 110 and a secondencapsulant 132 or package body 132 encapsulating semiconductor die 120.Encapsulant 130 may be configured such that the first encapsulant 131and the second encapsulant 132 are integrally formed.

Substrate encapsulant 131 encapsulates lateral surfaces of the leadframe 110 and is formed or provided to expose top and bottom surfaces ofthe lead frame 110 to the outside. In addition, substrate encapsulant131 is formed or provided to expose die pad protrusion 111 a and leadprotrusions 112 a of lead frame 110. In accordance with the presentembodiment, die pad protrusion 111 a and lead protrusions 112 a areformed to protrude outward such that lead bottom surfaces 112 c and diepad bottom surface 111 c lie on a different plane than substrate bottomsurface 131 b. Package body 132 encapsulates semiconductor die 120adjacent to substrate top surface 112 b. In some embodiments, the sidesurfaces of substrate encapsulant 131 and the side surfaces of packagebody 132 are substantially coplanar.

With reference to FIG. 1B, semiconductor package 100 can be mounted orattached to a next level of assembly 10, such as circuit board 10. Inone embodiment, circuit board 10 comprises a circuit pattern 11electrically connected to lead frame 110 of semiconductor package 100using conductive connective structures 20, such as solder balls 20. Inone embodiment, solder balls 20 are connected between circuit pattern 11and die pad protrusion 111 a of lead frame 110 and between circuitpattern 11 and lead protrusions 112 a. In accordance with the presentembodiment, solder balls 20 are connected to circuit pattern 11 so as tosurround the lateral surfaces or vertical surfaces of die pad protrusion111 a and lead protrusions 112 a. These attributes facilitatesemiconductor package 100 being more stably connected to circuit board10, thereby improving reliability of the assembly structure. In oneembodiment, a first solder structure electrically connects die padbottom surface 111 c to a first portion circuit pattern 11 and a secondsolder structure electrically connects a lead 112 to a second portion ofcircuit pattern 11, wherein the first solder structure has a greaterwidth than the second solder structure as illustrated, for example, inFIG. 1B. In one embodiment, the first solder structure extends entirelyacross die pad bottom surface 111 c as generally illustrated, forexample, in FIG. 1B. In a further embodiment, the first solder structuresurrounds lateral surfaces of the die pad protruding from the substratebottom surface, and the second solder structure surrounds lateralsurfaces of one of the plurality of leads protruding from the substratebottom surface.

In some embodiments, solder balls 20 connecting semiconductor package100 to circuit board 10 have a thickness d2 of about 150 microns orless. In some embodiments, solder balls 20 can be made of conductivematerials, such a tin/lead, leadless tin, and other similar materials asknown to those of skill in the art.

In summary, semiconductor package 100 according to the presentembodiment comprises die pad protrusion 111 a and lead protrusions 112 aprotruding to the outside of semiconductor package 100. Theseprotrusions better facilitate using conductive structures, such assolder balls 20 to electrically connect semiconductor package 100 to anext level of assembly, such as circuit board 10. In accordance with thepresent embodiment, the conductive structures surrounds the lateralsurfaces of die pad protrusion 111 a and lead protrusions 112 a toprovide a more stable physical and electrical connection betweensemiconductor package 100 and circuit board 10 thereby improving thereliability of the assembled structure (i.e., board-level reliability).

FIG. 2A illustrates a cross-sectional view of an electronic package 200or electronic package structure 200, such as a semiconductor package 200in accordance with another embodiment. FIG. 2B illustrates across-sectional view of electronic package 200 attached to a next levelof assembly, such as circuit board 10. In some embodiments,semiconductor package 200 includes a substrate 210, such as a lead frame210 and substrate encapsulant 131, electronic die 120, such assemiconductor die 120, and package body 132. In one embodiment,substrate encapsulant 131 and package body 132 are configured as anencapsulant structure 130. In one embodiment, substrate encapsulant 131encapsulates, covers, or encloses, for example, side portions of leadframe 210. Substrate encapsulant 131 includes a substrate top surface131 a and an opposing substrate bottom surface 131 b. Semiconductorpackage 200 is similar to semiconductor package 100 illustrated in FIGS.1A and 1B. Thus, the following description will focus more ondifferences between semiconductor package 100 and semiconductor package200.

In one embodiment, lead frame 210 includes a die pad 211 having a diepad top surface 21 la and an opposing die pad bottom surface 211 b, aplurality of leads 212 each having a lead top surface 212 a and anopposing lead bottom surface 212 b, and a plurality of conductive bumps213 disposed on die pad bottom surface 211 b and lead bottom surfaces212 b. In one embodiment, a portion of die pad bottom surface 211 b isformed having a plurality of pad portions 211 c separated by one or morerecesses. Stated another way, die pad bottom surface 211 b isintentionally formed with a plurality of recessed portions such that diepad bottom surface 211 b is not a continuous or substantially planarsurface in contrast to die pad bottom surface 111 c illustrated, forexample, in FIG. 1A. In accordance with the present embodiment, therecess between pad portions 211 c is encapsulated by substrateencapsulant 131. In one embodiment, parts of die pad bottom surface 211b and lead bottom surfaces 212 b are substantially co-planar thesubstrate encapsulant bottom surface 131 b or the bottom surface ofencapsulant 130 as illustrated, for example, in FIG. 2A.

In accordance with the present embodiment, pad portions 211 c areexposed to the outside of semiconductor package 200 and a conductivebump 213 is disposed on or adjacent the exposed die pad bottom surface211 b of pad portions 211 c. In one embodiment, a conductive bump 231 isdisposed on each pad portion 211 c of die pad 211. Stated another way,die pad 211 includes a plurality of conductive bumps 213 disposed alongdie pad bottom surface 211 b. In some embodiments, conductive bumps 213can be a solder or other similar materials. In accordance with thepresent embodiment, conductive bumps 213 are formed in a solder-on-pad(SOP) type configuration. In one embodiment, die pad 211 comprises aconductive material such as copper, a copper alloy, a plated material,combinations thereof, or other materials as known to those of skill inthe art.

In one embodiment, die pad 211 comprises a substantially rectangularplate shape having four sides and four corners, which may be rounded. Itis understood that other shapes may be used as well. In someembodiments, the outer periphery of die pad 211 can be reduced inthickness using, for example, etching or stamping techniques. Inaccordance with the present embodiment, semiconductor die 120 iselectrically connected to die pad 211 and plurality of leads 212 using,for example, conductive bumps 122. In one embodiment, more than onconductive bump 122 is used to electrically connect semiconductor die120 to die pad 211.

In one embodiment, plurality of leads 212 are spaced apart from theperipheral edge segments (e.g., four sides) of die pad 211 and canarranged in directions perpendicular to the peripheral edge segments.Each lead 212 is further spaced apart from other leads 212 so that theleads are electrically disconnected from each other in some embodiments.It is understood that in other embodiments, some of the leads 212 can beelectrically connected to each other in accordance with the requirementsof a particular system application. In accordance with the presentembodiment, each lead bottom surface 212 b is exposed to the outside ofsemiconductor package 200 and includes a conductive bump 213 disposed onthe exposed lead bottom surface 212 b surface as illustrated, forexample, in FIG. 2A.

In accordance with the present embodiment, conductive bumps 213 areplaced onto lead frame 210 prior to semiconductor package 200 beingattached to circuit board 10 with solder balls 20 so that solder balls20 are not directly attached to lead frame 210 as in previous packagestructures. In one embodiment, conductive bumps 213 and solder balls 20preferably comprise the same material. In other embodiments, conductivebumps 213 and solder balls 20 may comprise different materials. Inaccordance with the present embodiment, by placing conductive bumps 213onto lead frame 210 before attaching semiconductor package 200 to a nextlevel of assembly, semiconductor package 200 can be more easily andfirmly attached or connected to circuit board 10. This attributeprovides for a more stable assembled structure, which further improvesreliability. In an alternative embodiment, solder balls 20 can beadvantageously attached to conductive bumps 213 prior to or in advanceof the attachment of semiconductor package 200 to the next level ofassembly. In some embodiments, solder balls 20 can have a thickness d3of about 200 microns or less.

FIG. 3A illustrates a perspective plan view of an electronic package 300or electronic package structure 300, such as a semiconductor package 300in accordance with a further embodiment. FIG. 3B illustrates a partialcross-sectional view of semiconductor package 300 taken along referenceline 1-1′ of FIG. 3A. As illustrated in FIG. 3B, semiconductor package300 can be attached to, for example, a next level of assembly, such ascircuit board 10. In accordance with the present embodiment,semiconductor package 300 comprises a substrate 310, such as lead frame310 and substrate encapsulant 131, semiconductor die 120, and packagebody 132. In one embodiment, substrate encapsulant 131 and package body132 are configured as an encapsulant structure 130. Semiconductorpackage 300 is similar to semiconductor package 100 and semiconductorpackage 200 and the following description will focus more on thedifferences between semiconductor package 300 and semiconductor package100 and semiconductor package 200.

Lead frame 310 includes a die pad 311 having a die pad top surface 311 aand an opposing die pad bottom surface 311 b. In one embodiment, die pad311 comprises a substantially rectangular plate shape having four sidesand four corners, which may be rounded. It is understood that othershapes may be used as well. In some embodiments, the outer periphery ofdie pad 311 can be reduced in thickness using, for example, etching orstamping techniques. In one embodiment, die pad 311 comprises aconductive material such as copper, a copper alloy, a plated material,combinations thereof, or other materials as known to those of skill inthe art.

Lead frame 310 further comprises a plurality of leads 312 spaced apartfrom die pad 311. In one embodiment, plurality of leads 312 are spacedapart from the peripheral edge segments (e.g., four sides) of die pad311 and can be arranged in directions perpendicular to the peripheraledge segments. Each lead 312 is further spaced apart from other leads312 so that the leads are electrically disconnected from each other insome embodiments. It is understood that in other embodiments, some ofleads 312 can be electrically connected to each other depending on therequirements of a specific system application. In accordance with thepresent embodiment, each lead 312 includes a first lead portion 312 aand a second lead portion 312 b extending laterally away from first leadportion 312 a. In accordance with the present embodiment, second leadportion 312 b has a lower portion reduced in thickness. In oneembodiment, the lower portions of second lead portions 312 b are halfetched. In accordance with the present embodiment, first lead portion312 a includes a lead bottom surface 312 c exposed to the outside ofsemiconductor package 300 and second lead portion 312 b includes a leadtop surface 312 d configured to attach to or electrically connect withsemiconductor die 120. In one embodiment, first lead portion 312 a ispositioned at an outermost part of lead frame 310 and lead bottomsurface 312 c of first lead portion 312 a is exposed to the outside ofsemiconductor package 300. In one embodiment, lead bottom surface 312 cof first lead portion 312 a is a portion or surface configured toconnect to conductive structure 20 or solder ball 20 when semiconductorpackage 300 is assembled with or attached to circuit board 10.

Second lead portions 312 b are formed to extend from first lead portions312 a towards die pad 311. Since the lower portion of each second leadportion 312 b is reduced in thickness and filled, encapsulated, orcovered by encapsulant 130, such as substrate encapsulant 131, secondlead portion 312 b is not exposed to the outside of semiconductorpackage 300. Stated another way, the lower portion of each second leadportion 312 b is encapsulated by substrate encapsulant 131 orencapsulant structure 130. In accordance with the present embodiment,semiconductor die 120 is attached to lead top surface 312 d of secondlead portion 312 b. In one embodiment, conductive pads 121 onsemiconductor die 120 are electrically connected to second lead portions312 b and die pad top surface 311 a with conductive bumps 122. Inaccordance with the present embodiment, semiconductor die 120 ispositioned to overlap second lead portion 312 b but does not overlapfirst lead portion 312 a. Stated another way, peripheral surfaces 120 cof semiconductor die 120 are positioned on second lead portions 312 b,but peripheral surfaces 120 c do not overlap first lead portions 312 a.

In accordance with the present embodiment, a first connection point P1,at which each of the plurality of leads 312 and the circuit board 10 areconnected to each other, is positioned on lead bottom surface 312 c offirst lead portion 312 a, and a second connection point P2, at whicheach of the plurality of leads 312 and the semiconductor die 120 areconnected to each other, is positioned on lead top surface 312 d of eachsecond lead portion 312 b. Stated another way, the first connectionpoint P1 and the second connection point P2 are positioned to belaterally separated from each other. As described previously, the firstconnection point P1, at which each of plurality of leads 312 and circuitboard 10 are connected to each other, and the second connection pointP2, at which each of the plurality of leads 312 and the semiconductordie 120 are connected to each other, are positioned so as to not overlapeach other, thereby attaining improved results in assembled structurereliability tests.

For example, in a case of a conventional semiconductor package in whichthe first connection point P1 and the second connection point P2 overlapeach other, the conventional semiconductor package demonstrated 598cycles of temperature circulation endurance during board levelreliability tests. However, in a case of semiconductor package 300according to the present embodiment where the first connection point P1and the second connection point P2 do not overlap each other,semiconductor package 300 demonstrated 1104 cycles of temperaturecirculation endurance, which is about twice the temperature circulationendurance of the conventional package.

A temperature circulation endurance of a semiconductor package structureis tested by placing a semiconductor package in an enclosed chamber andinvestigating whether the semiconductor package is distorted or notwhile raising the temperature of the chamber to the highest temperatureor lowering the temperature of the chamber to the lowest temperature atregular intervals. In addition, a cycle typically corresponds to ameasurement period in which the internal temperature of the chamber israised from a reference temperature (e.g., room temperature) to thehighest temperature and is lowered to the lowest temperature to then beraised to the reference temperature.

In one embodiment, second lead portions 312 b are angled with respect tofirst lead portions 312 b as illustrated in FIG. 3A in order toaccommodate I/O pad layout configurations on semiconductor die 120. Inaddition, in one embodiment one or more second lead portions 312 b areof a different size or lateral width compared to other second leadportions 312 b as illustrated in FIG. 3A in order to accommodate morethan one I/O pad on semiconductor die 120.

In summary, in semiconductor package 300 first connection point P1,where each of the plurality of leads 312 and the circuit board 10 areconnected to each other, and the second connection point P1, where eachof the plurality of leads 312 and the semiconductor die 120 areconnected to each other, are positioned so as not to overlap each other,thereby improving the board level reliability of semiconductor package300.

It is understood that the features of semiconductor package 300 can beapplied to semiconductor packages 100 and 200 described previously.Also, the features of semiconductor package 100 can be applied to eithersemiconductor package 200 or 300 or the features can be combinedtogether in one semiconductor package.

In view of all of the above, it is evident that a novel structure andmethod is disclosed. Included, among other features, are protrusionstructures, conductive bump structures, and/or connection pointstructures configured to improve the board level or assembled structurereliability. More particularly, the features described herein singularlyor in various combinations reduce board level failures resulting fromtemperature circulation endurance tests, as well as others.

While the present invention has been particularly illustrated anddescribed with reference to exemplary embodiments thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and details can be made therein without departing from the spiritand scope of the present invention as defined by the following claims.By way of example, the semiconductor packages can be configured asmulti-chip packages. It is therefore desired that the presentembodiments be considered in all respects as illustrative and notrestrictive, reference being made to the appended claims rather than theforegoing description to indicate the scope of the invention.

As the claims hereinafter reflect, inventive aspects may lie in lessthan all features of a single foregoing disclosed embodiment. Thus, thehereinafter expressed claims are hereby expressly incorporated into thisDetailed Description of the Drawings, with each claim standing on itsown as a separate embodiment of the invention. Furthermore, while someembodiments described herein include some but not other featuresincluded in other embodiments, combinations of features of differentembodiments are meant to be within the scope of the invention and meantto form different embodiments as would be understood by those skilled inthe art.

What is claimed is:
 1. An electronic package structure comprising: asubstrate comprising: a die pad having die pad top surface and anopposing die pad bottom surface, wherein the die pad comprises aconductive material; a plurality of leads laterally spaced apart fromthe die pad; and a substrate encapsulant interposed between the die padand the plurality of leads, wherein the substrate encapsulant has asubstrate top surface and an opposing substrate bottom surface, andwherein the die pad and the plurality of leads protrude outward from thesubstrate bottom surface; an electronic die electrically coupled to thedie pad and the plurality of leads; and a package body encapsulating theelectronic die and the substrate top surface, wherein the substratebottom surface is exposed to the outside.
 2. The structure of claim 1,wherein the die pad bottom surface comprises a continuous andsubstantially planar surface.
 3. The structure of claim 1, wherein thedie pad bottom surface and the bottom surfaces of the leads protrudeoutward a distance of less than about 10 microns from the substratebottom surface.
 4. The structure of claim 1 further comprising a circuitboard electrically connected to the substrate through solder structuresand having a circuit pattern formed thereon.
 5. The structure of claim4, wherein: the die pad bottom surface comprises a continuous andsubstantially planar surface; a first solder structure electricallyconnects the die pad bottom surface to a first portion the circuitpattern; and a second solder structure electrically connects a lead to asecond portion of the circuit pattern, wherein the first solderstructure has a greater width than the second solder structure.
 6. Thestructure of claim 5, wherein the first solder structure extendsentirely across the die pad bottom surface.
 7. The structure of claim 4,wherein: a first solder structure surrounds vertical side surfaces ofthe die pad protruding from the substrate bottom surface; and a secondsolder structure surrounds vertical side surfaces of one of theplurality of leads protruding from the substrate bottom surface.
 8. Thestructure of claim 4, wherein the plurality of leads comprises: a firstlead portion exposed to the outside of the substrate bottom surface andattached to the circuit pattern at a first connection point; and asecond lead portion laterally extending towards the die pad and having arecessed bottom surface encapsulated by the substrate encapsulant, andwherein a conductive pad on the electronic die is attached to the secondlead portion at a second connection point, and wherein the firstconnection point is laterally separated from the second connectionpoint, and wherein the electronic die overlaps the second connectionpoint but not the first connection point.
 9. The structure of claim 1,wherein: the electronic die comprises a plurality of conductive pads ona major surface; the plurality of conductive pads are electricallycoupled to the plurality of leads and the die pad with conductive bumps;and more than one conductive bump connects the electronic die to the diepad.
 10. An electronic package structure comprising: a substratecomprising: a die pad having die pad top surface and an opposing die padbottom surface, wherein the die pad comprises a conductive material; aplurality of leads laterally spaced apart from the die pad each leadhaving a lead top surface and an opposing lead bottom surface; asubstrate encapsulant interposed between the die pad and the pluralityof leads, wherein the substrate encapsulant has a substrate top surfaceand an opposing substrate bottom surface; an electronic die electricallycoupled to the die pad and the plurality of leads; and a package bodyencapsulating the electronic die and the substrate top surface, whereinthe substrate bottom surface is exposed to the outside, and wherein thesubstrate further comprises one or more structural features configuredto improve board-level reliability, the one or more features comprisingone or more of: the die pad and the plurality of leads configured toprotrude outward from the substrate bottom surface such that sidesurfaces of the die pad and the plurality of leads are exposed to theoutside, conductive bumps disposed on the die pad bottom surface and thelead bottom surfaces, or at least one lead comprising: a first leadportion exposed to the outside of the substrate bottom surface anddefining a first connection point for attaching the electronic packagestructure to a next level of assembly; and a second lead portionlaterally extending towards the die pad and having a recessed bottomsurface encapsulated by the substrate encapsulant, the second leadportion defining a second connection point for attaching to theelectronic die, wherein the first connection point is laterallyseparated from the second connection point.
 11. The structure of claim10, wherein the one or more features includes the conductive bumps, andwherein the die pad bottom surface comprises a plurality of pad portionsseparated by a recess encapsulated by the substrate encapsulant.
 12. Thestructure of claim 11, wherein the die pad bottom surface and leadbottom surfaces are substantially co-planar with the substrate bottomsurface, and wherein a conductive bump is disposed on each pad portion.13. The structure of claim 10, wherein the one or more features includesthe die pad and the plurality of leads configured to protrude outwardfrom the substrate bottom surface, and wherein the die pad bottomsurface comprises a continuous and substantially planar surface.
 14. Thestructure of claim 10, wherein the one or more features includes the atleast one lead comprising the first lead portion and the second leadportion, wherein a conductive pad on the electronic die is attached tothe second lead portion at the second connection point, and wherein theelectronic die overlaps the second connection point but not the firstconnection point.
 15. The structure of claim 10, wherein: the electronicdie comprises a plurality of conductive pads on a major surface; theplurality of conductive pads are electrically coupled to the pluralityof leads and the die pad with conductive bumps; and more than oneconductive bump connects the electronic die to the die pad.
 16. Anelectronic package structure comprising: a substrate including a die padand a plurality of leads spaced apart from the die pad; an electronicdie electrically connected to the die pad and the plurality of leads;and an encapsulant structure encapsulating the substrate and theelectronic die, wherein a bottom surface of the die pad and bottomsurfaces of the plurality of leads are exposed to the outside, whereinthe electronic die is attached to first portions of the plurality ofleads to define first connection points, and wherein the plurality ofleads comprise second portions attached to the first portions, whereinthe second portions are configured to define second connection pointsfor attaching to a next level of assembly, and wherein the firstconnection points and the second connection points are laterallyseparated.
 17. The structure of claim 16, wherein the first portions ofthe plurality of leads are enclosed within the encapsulant, and whereinthe second portions are angled with respect to the first portions, andwherein at least one second portion has a larger width than anothersecond portion.
 18. The structure of claim 16, wherein the substratefurther comprises a substrate encapsulant interposed between the die padand the plurality of leads, and wherein the substrate encapsulant has asubstrate top surface and an opposing substrate bottom surface, andwherein the die pad bottom surface and the bottom surfaces of the leadsare exposed in the substrate bottom surface.
 19. The structure of claim18, wherein the die pad bottom surface and the bottom surfaces of theleads protrude outward from the substrate bottom surface to providelateral surfaces configured to engage solder structures along sidesurfaces of the die pad and leads.
 20. The structure of claim 19,wherein the die pad bottom surface comprises a continuous andsubstantially planar surface.